We tried the new North Carolina Motorsports Park today and had a blast! It is located in Henderson, NC. There were about 13-15 miles of muddy trails to explore, including a loop through a swamp. Terrain was also quite hilly in places. Winching was required in several mudholes. The park also has a race track (and child's track) and is in the process of opening a 2nd one along with more wooded trails. The gate fee is $20/per rider. I've posted a few pictures from the ride at the link below, as well as their site.

http://pg.photos.yahoo.com/ph/crazykayaker89/my_photos
http://www.ncmotorsportspark.com/